Russian shipbuilder Admiralty Shipyards will hand over the first of six submarines to Vietnam in November, Russian news agency RIA Novosti has reported.

"We are expecting the signing of the acceptance act and the sub's sailing to Vietnam in November," it quoted the shipyard as saying.

Vietnam ordered the submarines in 2009, with the contract, which also includes training for Vietnamese crews in Russia, said to be worth US$2 billion.

The delivery is expected to be completed by 2016.

The first submarine successfully completed 100-day trials in July and a Vietnamese crew has been training since April this year, the shipbuilder said.

"The vessel showed excellent maneuverability and reliable work of all mechanisms during the trials."

The underwater vessel belongs to the Varshavyanka class, an improvement on the Kilo which is described by the US Navy as "black holes in the ocean" because they are "nearly undetectable when submerged."

The Varshavyanka class has more advanced stealth technology and an extended combat range, the RIA Novosti report said.